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United States Patent |
5,679,820
|
Pickett
,   et al.
|
October 21, 1997
|
Silylated ultraviolet light absorbers having resistance to humidity
Abstract
The instant invention is directed to novel silylated agents having the
formula
##STR1##
where Ar and Ar' are independently substituted or unsubstituted aromatic
rings, R is a branched or unbranched chain of 1 to 6 carbons, R' and R"
are independently C1 to C12 alkyl or mixtures of C1 to C12 alkyl, and n is
1 or 2. The novel dibenzoylresorcinol silylated agents are capable of
absorbing ultraviolet light.
Inventors:
|
Pickett; James Edward (Schenectady, NY);
Gillette; Gregory Ronald (Clifton Park, NY)
|
Assignee:
|
General Electric Company (Schenectady, NY)
|
Appl. No.:
|
766655 |
Filed:
|
December 16, 1996 |
Current U.S. Class: |
556/436; 106/287.14; 428/412; 428/447 |
Intern'l Class: |
C07F 007/08; C07F 007/18 |
Field of Search: |
556/436
106/287.14
428/412,447
|
References Cited
U.S. Patent Documents
5214085 | May., 1993 | Patel et al.
| |
5391795 | Feb., 1995 | Pickett.
| |
5606089 | Feb., 1997 | Tamura et al. | 556/436.
|
Primary Examiner: Shaver; Paul F.
Attorney, Agent or Firm: Johnson; Noreen C., Pittman; William H.
Claims
What is claimed:
1. A silylated agent having the formula
##STR5##
where Ar and Ar' are independently substituted or unsubstituted aromatic
rings, R is a branched or unbranched chain of carbons, R' and R" are
independently C1 to C12 alkyl or mixtures of C1 to C12 alkyl, and n is 1,
2, or 3.
2. A silylated agent in accordance with claim 1 where said agent is
4,6-dibenzoyl-2-(alkoxysilylalkyl) resorcinol.
3. A silylated agent in accordance with claim 1 where said agent is
4,6-dibenzoyl-2-(3-alkoxysilylpropyl) resorcinol.
4. A silicone hardcoat comprising:
a silylated agent having the formula
##STR6##
where Ar and Ar' are independently substituted or unsubstituted aromatic
rings, R is a branched or unbranched chain of carbons, R' and R" are
independently C1 to C12 alkyl or mixtures of C1 to C12 alkyl, and n is 1,
2, or 3; and
a silicone compound containing composition.
5. A silicone hardcoat in accordance with claim 4 wherein said silicone
compound containing composition has the formula
RSi(OR).sub.3,
where each R is independently an alkyl group having 1 to 3 carbon atoms or
a substituted or unsubstituted aromatic radical.
6. A silicone hardcoat in accordance with claim 5 wherein each R is a
methyl group.
7. A silicone hardcoat in accordance with claim 4 where said silylated
agent is 4, 6-dibenzoyl-2-(alkoxysilylalkyl) resorcinol.
8. A silicone hardcoat in accordance with claim 4 where said silylated
agent is 4, 6-dibenzoyl-2-(3-alkoxysilylpropyl) resorcinol.
9. A solid substrate with a silicone hardcoat applied thereon where said
silicone hardcoat comprises:
a silylated agent having the formula
##STR7##
where Ar and Ar' are independently substituted or unsubstituted aromatic
rings, R is a branched or unbranched chain of carbons, R' and R" are
independently C1 to C12 alkyl or mixtures of C1 to C12 alkyl, and n is 1,
2, or 3; and
a silicone compound containing composition.
10. A solid substrate in accordance with claim 9 where said silicone
compound containing composition has the formula
RSi(OR).sub.3,
where each R is independently an alkyl group having 1 to 3 carbon atoms or
a substituted or unsubstituted aromatic radical.
11. A solid substrate in accordance with claim 10 where each R is a methyl
group.
12. A solid substrate in accordance with claim 9 where said silylated agent
is 4,6-dibenzoyl-2-(alkoxysilylalkyl) resorcinol.
13. A solid substrate in accordance with claim 9 where said silylated agent
is 4,6-dibenzoyl-2-(3-alkoxysilylpropyl) resorcinol.
14. A solid substrate in accordance with claim 9 where said solid substrate
is a polycarbonate.
15. A solid substrate in accordance with claim 14 where said polycarbonate
is a homopolycarbonate.
16. A solid substrate in accordance with claim 14 where said polycarbonate
is a copolycarbonate.
17. A solid substrate in accordance with claim 14 where said polycarbonate
is bisphenol A polycarbonate.
18. A solid substrate in accordance with claim 9 where said substrate is
treated with a primer prior to applying said silicone hardcoat.
19. A UV curable acrylic coating comprising:
a compound useful for absorbing ultraviolet light having the formula
##STR8##
where Ar and Ar' are independently substituted or unsubstituted aromatic
rings, R is a branched or unbranched chain of carbons, R' and R" are
independently C1 to C12 alkyl or mixtures of C1 to C12 alkyl, and n is 1,
2, or 3; and
a substantially transparent matrix composition.
20. A coating according to claim 19 where said transparent matrix is
selected from the group consisting of acrylics, urethanes, melamines, and
mixtures thereof.
21. A solid substrate with a UV curable acrylic coating composition applied
thereon wherein said coating composition comprises:
a compound useful for absorbing ultraviolet light having the formula
##STR9##
where Ar and Ar' are independently substituted or unsubstituted aromatic
rings, R is a branched or unbranched chain of carbons, R' and R" are
independently C1 to C12 alkyl or mixtures of C1 to C12 alkyl, and n is 1,
2, or 3; and
a substantially transparent matrix composition.
Description
FIELD OF THE INVENTION
This invention relates to novel silylated compositions capable of absorbing
ultraviolet light and methods of making the compositions. Particularly,
the compositions are dibenzoyl alkoxysilylalkyl resorcinols having less
than three alkoxy groups on the silicon which are photostable and
compatible in silicone hardcoat matrices.
BACKGROUND OF THE INVENTION
Thermoplastic substrates such as polycarbonates are generally characterized
by many advantageous properties which include clarity, high ductility,
high heat deflection temperature, as well as dimensional stability. Many
of these materials are transparent and are conventionally employed as
replacements for glass in commercial applications.
While thermoplastic resins possess the above-described advantageous
properties, they often display low abrasion and chemical solvent
resistances, and like many other organic polymeric materials, they are
susceptible to degradation by ultraviolet light. This results in
unfavorable characteristics including yellowing and erosion of the
substrate surface.
Recently, it is of increasing interest to prepare resinous thermoplastic
substrates, such as polycarbonates, that are resistant to abrasion and
photodegradation. This is often accomplished by treating the substrate
surface with a silicone hardcoat material, whereby the coating material
typically contains ultraviolet light absorbing agents, such as
benzotriazoles and benzophenones, and hindered amine light stabilizers.
It is often discovered, however, that the ultraviolet light absorbing
compounds (herein also referred to as UV absorbers), themselves, decompose
upon exposure to ultraviolet light. Prolonged exposure to sunlight,
moisture and thermal cycling conditions can cause yellowing, delamination
and formation of microcracks in the coating material, decreasing
transparency. This leads to a degradation of the favorable properties of
the thermoplastic substrate which the UV absorbers are originally employed
to protect. Thus, there is an ongoing need to seek new, efficient UV
absorbing compounds for use in abrasion resistant, highly weatherable
coatings.
In commonly owned and assigned U.S. Pat. No. 5,391,795, incorporated herein
by reference, there is disclosed a UV absorber based on
4,6-dibenzoylresorcinol bearing a trialkoxysilyl group on a short alkyl
chain as shown by the formula
##STR2##
The above-mentioned UV absorber has excellent photostability due to the
chromophore in the silicone hardcoat matrix. It was thought that the
trialkoxygroup was essential for good compatibility and abrasion
resistance. It has since become apparent that the trialkoxysilane
derivatives suffer from poor hydrolytic stability. This is observed when
the solid silylated UV absorber is allowed to be in contact with moist air
for periods as little as a 2 to 3 days to several weeks. A solid crust
forms on the silylated UV absorber which does not dissolve in the silicone
hardcoat coating composition. While the insoluble material can be filtered
off, some of the UV absorber is lost. Thus, there is also a need to
develop derivatives based on 4,6-dibenzoylresorcinol which would have
improved shelf stability while still making coatings with good abrasion
resistance, UV absorbance, and excellent weatherability.
SUMMARY OF THE INVENTION
The instantly claimed invention satisfies these needs by providing novel
dibenzoylresorcinol silylated agents capable of absorbing ultraviolet
light. The silylated agents are 4,6-dibenzoyl-2-(dialkoxysilylalkyl)
resorcinols or 4,6-dibenzoyl-2-(monoalkoxysilylalkyl) resorcinols which
display photostability, compatibility in silicone hardcoat and UV curable
acrylic matrices, and improved hydrolytic stability.
In a first aspect, the instant invention is directed to novel silylated
agents having the formula
##STR3##
where Ar and Ar' are independently substituted or unsubstituted aromatic
rings, R is a branched or unbranched chain of carbons, R' and R" are
independently C1 to C12 alkyl or mixtures of C1 to C12 alkyl, and n is 1,
2, or 3. A preferred amount of carbons for R is 1 to 6 carbons. Often, the
silylated agent is a 4,6 dibenzoyl-2-(alkoxysilylalkyl) resorcinol and
preferably, 4,6-dibenzoyl-2-(3-alkoxysilylpropyl) resorcinol.
In a second aspect of the instant invention, the novel silylated agents
described above are incorporated into thermally cured silicon
compound-containing compositions. Said compositions comprising the
silylated agents are coating compositions defined as silicone hardcoats or
topcoats.
In a third aspect of the invention, the novel silylated agents described
above are incorporated into UV-curable acrylic coating compositions. The
coating compositions are defined as coatings comprising the silylated
agents and a substantially transparent matrix composition. Generally, the
matrix material contains acrylics, urethanes, melamines, or mixtures
thereof. Copending and commonly assigned U.S. patent application Ser. No.
08/699,254, filed Aug. 15, 1996, herein incorporated be reference, also
describes coating compositions.
In a fourth aspect of the instant invention, the above described silicone
hardcoats or UV-curable coatings are applied to the surface of a solid
substrate thus producing a coated solid substrate having improved
resistances to abrasion and ultraviolet light. Such coated solid
substrates are often referred to as weatherable substrates. Further, there
are no limitations with respect to the thickness of the coatings applied
to said solid substrates. They are, however, often about 0.5 to about 50
.mu.m thick and preferably about 3 to about 15 .mu.m thick. In the instant
invention, the solid substrates that may be employed often include polymer
substrates such as acrylic polymers including poly (methyl methacrylate),
polyesters such as poly (ethylene terephthalate) and poly(butylene
terephthalate), polyamides, polyimides, acrylonitrile-styrene copolymers,
styrene-acrylonitrile-butadiene copolymers, polyvinyl chloride,
polystyrene, blends of polystyrene and polyphenylene ethers, butyrates,
polyethylene and the like. Thermoplastic substrates can be with or without
pigments. Moreover, said solid substrates may also include metal
substrates, painted surfaces, glass, ceramics and textiles. However, the
coating compositions of the instant invention are preferably employed to
coat polycarbonates.
Those skilled in the art will gain a further and better understanding of
the present invention from the detailed description set forth below,
considered in conjunction with the examples and chemical drawings
accompanying and forming a part of the specification.
DETAILED DESCRIPTION OF THE INVENTION
It is discovered that dibenzoylresorcinol derivatives based on formula II
can be prepared that have fewer than three alkoxy groups on the silicon
yet still have excellent compatiblity in silicone hardcoat resins and
surprisingly excellent abrasion resistance upon cure. In addition,
derivatives with only one or two alkoxy groups have improved compatibility
after exposure to moist air indicating better shelf stability of the
materials.
In Formula II,
##STR4##
Ar and Ar' are independently substituted or unsubstituted aromatic rings, R
is a branched or unbranched chain carbons, R' and R" are independently C1
to C12 alkyl or mixtures of C1 to C12 alkyl, and n is 1, 2, or 3. The
preferred number of carbons for R is 1 to 6. The derivative with n=0 is
the prior-art compound. The derivative with n=3 can be prepared, but its
initial solubility may be limited in the coatings. Certain silyl
derivatives are conveniently prepared by the hydrosilylation of the
appropriate allyl or substituted allyl 4,6-dibenzoylresorcinol as shown in
the Example 3 of the above-mentioned U.S. Pat. No. 5,391,795.
Preparation of the novel silylated agents, 4,6-dibenzoyl-2-(di or
monoalkoxysilylalkyl) resorcinols employed in the instant invention is
achieved, for instance, by first mixing a benzoyl halide and an aluminum
halide in an organic solvent with a dialkoxybenzene to produce a
4,6-dibenzoylresorcinol. The 4,6-dibenzoylresorcinol is subsequently
subjected to a quaternary ammonium salt and an allyl halide under basic
conditions to produce a 2-allyl-4,6-dibenzoylresorcinol. The 2-allyl
4,6-dibenzoylresorcinol is contacted with a alkoxyhydrosilane in the
presence of a hydrosilylation catalyst in order to produce the desired
4,6-dibenzoyl-2-(di or mono-alkoxysilylalkyl)resorcinol.
The preparation of the novel silylated agents of the instant invention is
further illustrated by the following examples. Molecular structures of all
products in the examples may be confirmed by proton and carbon-13 nuclear
magnetic resonance spectroscopy.
EXAMPLES
Example 1
Preparation of Silylated UV Absorbers
2-Allyl-4,6-dibenzoylresorcinol (10.75grams, 30 mmol) was suspended in 40
milliliters of toluene. To this was added 2 drops of Karstedt's catalyst
(complex of platinum in 1,3-divinyl-tetramethyldisiloxane) and the
temperature was brought to 65.degree. C. whereupon 35 mmol of the
appropriate silane (shown in Table 1) was added. The temperature was held
at about 65.degree. to 85.degree. C. for about 1 to 2 hours after which
the reaction mixture was cooled, filtered, and evaporated to give amber
oils which solidified upon cooling. The NMR spectra of the products were
fully consistent with the expected structure. The yields are shown in
Table 1. The products are Formula II where Ar and Ar' are phenyl, R is
CH.sub.2 CH.sub.2 CH.sub.2, R' is ethyl and R" is methyl.
TABLE 1
______________________________________
Yield of silylated dibenzoylresorcinol of formula II
Entry
# Hydrosilane
R R' R n Yield
______________________________________
1 HSi(OEt).sub.3
CH.sub.2 CH.sub.2 CH.sub.2
Et -- 0 94%
2 HSiCH.sub.3 (OEt).sub.2
CH.sub.2 CH.sub.2 CH.sub.2
Et Me 1 94%
3 HSi(CH.sub.3) .sub.2 OEt
CH.sub.2 CH.sub.2 CH.sub.2
Et Me 2 98
4 HSi(Et).sub.3
CH.sub.2 CH.sub.2 CH.sub.2
-- Et 3 72%
______________________________________
Example 2
Testing for Resistance to Humidity
1.0 gram samples of silylated dibenzoylresorcinol (DBR) derivatives 1
through 3 of Table 1 were ground to course powders and placed in aluminum
pans above a dish of water in a dessicator to simulate extended exposure
to moist air. After 24 days of exposure at room temperature, 0.50 gram
portions of each was added to 20 gram samples of a silicone hardcoat resin
(GE Silicones AS4004, 25% resin solids) and stirred overnight at room
temperature. The resins were then filtered on 10-20 micron fritted glass
funnels to measure the amount of insoluble material. The residues were
dried to constant weight in a vacuum oven at about 140.degree. C.
TABLE 2
______________________________________
Insolubles in coating resins prepared from "aged" UV absorbers.
Entry silated DBR Weight of insolubles
Percent
# from Table 1 (grams) insoluble
______________________________________
1 1 0.241 48%
2 2 0.001 0.2%
3 3 0.009 1.8%
______________________________________
Hardcoat formulations prepared with fresh silylated derivatives 1, 2 and 3
had only trace amounts of insolubles while derivative #4 was essentially
insoluble in the coating solution. It can be seen that derivatives 2 and 3
had much improved resistance to the formation of insoluble residues
compared with prior-art derivative 1.
Example 3
Coated Polycarbonate Panels
Coating resins were prepared as in Example 2 using fresh silylated
derivatives 1, 2, and 3. These were filtered (removing only traces of
insoluble materials). Lexan.RTM., a registered trademark of General
Electric Company, polycarbonate panels (4".times.12".times.1/8") were
washed with isopropyl alcohol, dried, and primed by flowcoating with an
aqueous acrylic emulsion primer. The primed panels were baked at about
128.degree. C. in an air oven for about 60 minutes. The cooled panels were
then flow coated with the coating resins, air dried for about 30 minutes,
and baked at about 128.degree. C. for about 60 minutes. The resulting
coatings were substantially defect-free and optically clear. The center 4
inches of the panels were subjected to the Taber abrasion test (ASTM
D1044-94) using CS-10F wheels for 500 cycles under 500 gram load. The
results shown on Table 3 indicate substantially equivalent abrasion
resistance within the error limits of the test. This is surprising in view
of the commonly-held belief that use of di or mono-alkoxysilanes would
lead to significantly decreased abrasion resistance.
TABLE 3
______________________________________
Abrasion resistance of hardcoated polycarbonate panels
Entry DBR-silane
% Haze after
# from Table 1
Taber test
______________________________________
1 1 10
2 2 12
3 3 11
______________________________________
Example 4
UV-curable Coatings
Coating formulations were prepared as shown below in Table 4.
TABLE 4
______________________________________
Coating compositions (parts by weight)
Component
A B C D
______________________________________
Polyurethane hexacrylate (Ebecryl .RTM. 1260)
8 8 8 8
FCS100 (GE Silicones acrylated colloidal
2 2 2 2
silica)
Tinuvin .RTM. 123 (Ciba Geigy)
0.1 0.1 0.1 0.1
Surfactant 0.01 0.01 0.01 0.01
5 5 5 5
2,4,6-trimethylbenzoyl diphenyl phosphine
0.3 0.3 0.3 0.3
oxide (initiator)
Isopropyl alcohol/propylene glycol
20 20 20 20
monomethyl ether (1:1)
Aged DBR-silane 1 (Table 1)
0.5 -- -- --
Aged DBR-silane 2 (Table 1)
-- 0.5 -- --
Aged DBR-silane 3 (Table 1)
-- -- 0.5 --
DBR-silane 4 (Table 1) 0.5
______________________________________
The formulations were stirred in the dark for three days and then flow
coated onto pre-cleaned Lexan.RTM. polycarbonate panels. The resulting
coatings were air dried for one minute, dried at about 70.degree. C. for
four minutes, and then exposed to UV light by passing them five times
under two 300 watt/inch medium pressure mercury lamps using a conveyor
moving at about 25 ft/min. The initial haze of the resulting coatings as
well as the haze of the coating solutions (in a 1 cm cell) are shown in
Table 5. UVA 4 in composition D was essentially insoluble.
TABLE 5
______________________________________
Haze of coating solutions and cured coatings
Formulation
(Table 4) % Haze of coating
% Haze of solution
______________________________________
A 1.4 97.3
B 0.4 7.6
C 0.9 37.8
D 11.9 --
______________________________________
The coating prepared with Formulations A and D had unacceptable optical
quality due to large amounts of insoluble material in the coating
solution. Formulations prepared identically with A, B, and C using unaged
UVA 1, 2, and 3 respectively gave essentially clear solutions and
haze-free coatings.
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